This invention relates to a compressed air braking system and more particularly to an air dryer assembly used to remove moisture entrained in the air.
Trucks, buses, and related heavy-duty vehicles often employ an air braking system in which compressed air from a source or storage reservoir is selectively applied and released from brake chambers associated with the wheels. It is important to control the moisture content of the compressed air, particularly because moisture can adversely affect operation of the braking system. Air dryers are commonly used to remove the moisture from the compressed air.
The air dryer includes a desiccant material, such as desiccant beads, enclosed in a cavity through which the compressed air is introduced. Since the desiccant material adsorbs moisture, it is necessary to periodically regenerate the desiccant material by a purge flow. Although effective for some period of time, the desiccant material breaks down over time and requires occasional replacement. Thus, it is desirable that air dryer be easily assembled and disassembled.
In addition, voids in the desiccant bed or non-compacted regions of desiccant can lead to premature breakdown or powdering of the desiccant beads. Therefore, a loading force across the desiccant bed which assures compression and/or compaction which, in turn, prolongs the useful life of the desiccant beads.
It is also known that under non-uniform compression, the desiccant material will not flow from a high-pressure area to a low pressure area without an additional, constantly applied force. To maximize the effective operation of the desiccant, it is thus desirable to uniformly load the desiccant bed and thereby minimize areas of non-flow.
It is also known that desiccant beds shift during use. Flexibility is required to permit this shifting and to date known structures do not effectively address this concern. Thus it is important to allow shifting while still uniformly compacting the desiccant bed. Structures to date have not effectively achieved these goals.
In conjunction with even force application and accommodating movement of the desiccant bed, it is necessary to maintain separate inlet and outlet air paths or passages in a manner that still achieves the above goals.
Accordingly, a need exists for an improved compressed air dryer assembly that provides a reliable assembly and advantageously achieves these results in an economic manner.